The present invention relates to an optical system including an arrangement for splitting light into a plurality of light guides for directing light, e.g., downwardly from a ceiling fixture.
Fiberoptic systems offer many advantages over conventional electric lighting directional lighting systems. These include delivery of light without the heat generated by the light source, the absence of ultraviolet light, controllability, the use of simple and compact lighting fixtures, the absence of electrical wiring at the lighting point, increased life, etc. Unfortunately, improved efficacy over conventional lighting is not yet one of the advantages of commercially available fiberoptic systems. The following example illustrates the present situation: A conventional MR-16 Track lighting system using four 50-watt light sources would consume 200 watts (lamps) and 40 watts (transformer power supply) while delivering about 600xc3x974 (or 2400) lumens, for an overall delivered system efficacy of about 10 lumens per watt. State of the art 150-watt metal halide fiberoptic systems might deliver 363 lumens in each of four remote points (e.g., 3 meters) consuming 150 watts (lamp) and 60 watts (power supply and fan) for total efficacy of about 7 lumens per watt.
Because of increased international concern over reduction in energy usagexe2x80x94and thus the desire to foster the use of energy efficient lightingxe2x80x94as well as the practical concern of lowering operating costs, it would be desirable for fiberoptic systems to achieve increased efficiency over conventional directional lighting sources. This should be possible, in principle, since metal halide light sources now commonly in use in fiberoptic applications typically have four times the efficiency of conventional halogen light sources. The inherent efficiency gain in using a metal halide light source, however, is lost in the inefficiencies of conventional imaging collection (e.g., elliptical reflector) and distribution approaches (e.g., bundled fibers) used in the architecture of such systems.
An exemplary embodiment of the invention comprises an efficient system for directing light, which includes a light source and a generally tubular, hollow coupling device with an interior light-reflective surface for receiving light from the source at an inlet and transmitting it as a generally diverging beam through an outlet. The coupling device is shaped in accordance with non-imaging optics and increases in cross sectional area from inlet to outlet in such manner as to reduce the angle of light reflected from the surface as it passes through the device. A thermal-isolating region has an inlet positioned in proximity to an outlet of the coupling device and has an outlet for passing light to an optical member. An arrangement for splitting the light from the outlet of the thermal-isolating region comprises a plurality of light guides. Each light guide includes an inlet end for receiving light from the thermal-isolating region and an outlet end for directing light to a remote location. The inlet ends are substantially coplanar with each other and form a substantially solid shape. The coupling device and thermal-isolating region are shaped so as to distribute a respective, substantial (i.e., useful) amount of light to each of the plurality of light guides.
The foregoing system typically achieves a high degree of efficacy (e.g., 30 lumens per watt) while being compact.